The present invention relates to an implantable drainage valve for the treatment of hydrocephalus, and more particularly to such a valve of the type comprising a body forming a valve seat, a closing element, a spring arranged so as to press the closing element onto the seat, and a feeder compensating for differences in the height of the liquid column depending on the position of the patient carrying the valve.
There are already known various kinds of valves designed to control the drainage of excess cerebrospinal fluid from inside the cerebral ventricles into, for example, the peritoneal cavity.
Thus document EP-A-0617975 describes such a valve comprising a body forming a valve seat, a closing element such as a ball, and a spring, one end of which presses the closing element onto the body, ie. a flap-type valve. In this document, the valve also comprises a feeder on which bears the opposite end of the spring to the closing organ.
With such a valve it is possible to take into account differences in the height of the liquid column depending on the position, notably sitting or lying down, of the patient. For when the valve is in a horizontal position, the ball is only subjected to the upstream/downstream differential pressure and to the force exerted by the spring. In the vertical position, however, the feeder, whose weight is greater than the force of the spring, slightly compresses the latter, and its weight acts in place of the force of the spring, pushing the ball onto its seat, consequently with a greater force.
Although this valve is generally speaking satisfactory, it presents the drawback that in a vertical position, the feeder can move around to a certain extent within its housing. There may result undesirable dynamic or ballistic effects during jerky movement such as running, dynamic effects which may jeopardize the satisfactory functioning of the device.